CNBC/screengrab
Donald Trump.
Harwood, listing off some of Trump's various policy proposals involving immigration and tax reform, turned to the tycoon.
"Mr. Trump, you've done very well in this campaign so far by promising to build a wall and make another country pay for it, send 11 million people out of the country, cut taxes $10 trillion without increasing the deficit, and make Americans better off because your greatness would replace the stupidity and incompetence of others," Harwood said.
"Let's be honest," he added. "Is this a comic-book version of a presidential campaign?"
Trump said it wasn't, adding that he didn't think it was a very "nicely asked question."
The billionaire businessman cited conservative CNBC commentator and economist Larry Kudlow, who has said he said loves Trump's tax plan. He then proceeded to defend his plans to build a giant wall along the US-Mexican border.
"And Mexico is going to pay for the wall. … People say, 'Oh, how are you going to get Mexico to pay,'" Trump said. "A politician cannot get them to pay. I can."
Harwood then pressed Trump with a tough follow-up.
"I talked to economic advisers who have served presidents of both parties. They said that you have as much chance of cutting taxes that much without increasing the deficit as you would of flying away from that podium by flapping your arms," he told Trump.
Trump again cited Kudlow's praise for his plan.